Building the bioprinter was a multi-team process coordinating both the bioink composition team and hardware team. We considered the user interface and limitations of our modifications and compromised to produce a prototype that could extrude the bioink. Our next steps would controlling the bioprinter environment to optimize sterility and cell viability.
The Bioprinter
CAD Mockup of TronXY Moore 1 printer with planned modifications added: syringe pump and bioink reservoir.
The Pieces of our Bioprinter
Our bioprinter consists of three main pieces: A TronXY Moore 1 printer, a syringe pump which is mounted on the top of the bioprinter, and a bioink resevoir mounted on the side.
The Tronxy Moore 1 printer is a clay printer we were allowed to use by a member of the lab. This printer needed several modifications made to it for our project. The current dispense mechanism on the Tronxy Moore 1 dispenses too large a volume for our purposes. Were we to use this volume we would encounter premature crosslinking from our bioink. This is why we have the syringe pump.
The syringe pump was adapted from last year. In the previous year it had been built to allow for future adaptations so syringes of different sizes could be used.
This is the syringe pump from the team’s previous season. This image is missing two parts: the syringe adaptor and syringe driver, the two modifiable pieces.
Early on in the season this piece was modified to fit a 10mL syringe, with the intention that it be used in the bioink extrusion experiments. This did not end up happening but it was re-used later in the season and made to fit a 50mL syringe.
In this version the addition of the parts allowing for the 50mL syringe to be loaded can be seen. These are the syringe driver (the added piece towards the back which holds the plunger of the syringe) and the syringe adapter (the additional piece towards the front where the front of the syringe is braced).
The syringe pump allows us to more precisely control the volume of the bioink being printed. This functions using a NEMA stepper motor screwed onto the back of the part. It controls a linearizer, which transforms the rotational force created by the motor into a forward force, which we use to push the plunger of the syringe pump forward. Our intention was to control this NEMA with an Arduino UNO and DRV8825 driver module.
The purpose of the bioink reservoir is to hold additional bioink to allow for simpler storage in two test tubes. This would be used to load the 50mL syringe which goes in the bioprinter. The two places for tubes to be put also means that the Martian regolith can be stored separately from the bioink to prevent crosslinking.
This holder is compatible for 50 mL falcon tubes which we will be using to store excess bioink during extrusion and printing.
Together the pieces all come together to form our bioprinter. Images from our actual build can be seen below.
Images from the build of the bioprinter.
The bioprinter functions by the arduino uno on the syringe pump pushing the NEMA stepper motor forward. This pushes the ink through the extruder on the printer itself, allowing printing to happen.
Future Work
By the end of the season our bioprinter had a delayed validation stage within this season due to a series of issues with power to the stepper motor. In the future we would want to build our own novel bioprinter to allow us full control over the features. As far as our modified bioprinter goes: It lacks mobility and versatility. It is a heavy system which is not necessary for our applications. A closed system prevents users from making necessary maintenance or modifications. This system cannot be repairable for users in the long run. The firmware on this device is not capable of remote activation, which means that for a Mars application it would need to be operated in-person, something that is inconvenient or a down-right nonstarter. This device does not have sterility capabilities nor does it have the ability to maintain sterility. With bacteria in use, it becomes increasingly difficult to maintain sterile conditions. The Tronxy extrusion system is not optimized for our ink and as such it faces issues with clogging due to the viscous nature of our bioink. A lower cost version of the bioprinter could be made, allowing for more access to the technology, particularly if it were made open source.
In conclusion, we learned a lot from the creation of our bioprinter but know that more could be done in the future to optimize it. We plan to build our own bioprinter instead of adapting off an old FDM or clay printer by building a customized 3D printer and replacing certain parts to tailor it for bioink instead of plastic.
